Quarterly report pursuant to Section 13 or 15(d)

Goodwill and Other Intangible Assets - Other Intangible Assets (Details)

v3.19.1
Goodwill and Other Intangible Assets - Other Intangible Assets (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2019
Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]    
Intangible Assets $ 659,473 $ 649,261
Accumulated Amortization (386,403) (372,081)
Intangible Assets, Net $ 273,070 277,180
Remaining Weighted Average Amortization Period in Years 7 years 9 months 18 days  
Indefinite-lived Intangible Assets [Line Items]    
Intangible Assets $ 662,473 652,261
Intangible Assets, Net 276,070 280,180
Engineering license    
Indefinite-lived Intangible Assets [Line Items]    
Intangible Assets 3,000 3,000
Customer relationships    
Finite-Lived Intangible Assets [Line Items]    
Intangible Assets 358,177 359,967
Accumulated Amortization (172,528) (165,715)
Intangible Assets, Net $ 185,649 194,252
Remaining Weighted Average Amortization Period in Years 5 years 10 months 24 days  
Backlog    
Finite-Lived Intangible Assets [Line Items]    
Intangible Assets $ 136,780 135,578
Accumulated Amortization (135,348) (134,592)
Intangible Assets, Net $ 1,432 986
Remaining Weighted Average Amortization Period in Years 8 months 12 days  
Trade names    
Finite-Lived Intangible Assets [Line Items]    
Intangible Assets $ 82,254 81,058
Accumulated Amortization (22,916) (21,559)
Intangible Assets, Net $ 59,338 59,499
Remaining Weighted Average Amortization Period in Years 15 years 2 months 12 days  
Non-compete agreements    
Finite-Lived Intangible Assets [Line Items]    
Intangible Assets $ 40,797 40,728
Accumulated Amortization (29,905) (30,168)
Intangible Assets, Net $ 10,892 10,560
Remaining Weighted Average Amortization Period in Years 3 years 3 months 18 days  
Patented rights and developed technology    
Finite-Lived Intangible Assets [Line Items]    
Intangible Assets $ 32,017 22,482
Accumulated Amortization (24,597) (19,175)
Intangible Assets, Net $ 7,420 3,307
Remaining Weighted Average Amortization Period in Years 2 years 7 months 6 days  
Curriculum    
Finite-Lived Intangible Assets [Line Items]    
Intangible Assets $ 9,448 9,448
Accumulated Amortization (1,109) (872)
Intangible Assets, Net $ 8,339 $ 8,576
Remaining Weighted Average Amortization Period in Years 8 years 9 months 18 days